| Johnson Granite Porphyry | |
|---|---|
| Stratigraphic range: 85.4 Ma | |
| Type | Geological formation |
| Area | 1,100 square kilometres (420 sq mi) |
| Location | |
| Location | Yosemite National Park |
| Country | United States of America |
| Type section | |
| Named for | Johnson Peak |
| Location | Yosemite National Park |
Johnson Granite Porphyry is found in Tuolumne Meadows, Yosemite National Park.
Johnson Granite Porphyry was named for Johnson Peak, the highest mountain in Tuolumne Meadows, Yosemite National Park.
Its area is estimated at 1,100 square kilometres (420 sq mi), the exposed area covering roughly 40 square kilometres (15 sq mi). Johnson Granite Porphyry is part of the Tuolumne Batholith. Its boundaries are difficult to trace, and are irregular. It is both the youngest, and the most siliceous rock of Tuolumne Intrusive Suite.
Geology
The innermost, most felsic part of the Tuolumne Batholith is the Johnson Granite Porphyry. It is a highly irregular, elongated body. Completely surrounding it is the much larger body of Cathedral Peak granite.
Field observations and magnetic fabrics suggest an extrusive event, that is, Johnson Granite Porphyry may record possible volcanism. This may relate to deformation along active shear zones.
Johnson Granite Porphyry is composed of
- quartz
- K-feldspar
- zoned plagioclase, and
- locally contains coarse-grained feldspars
- Biotite, the only mafic mineral, with accessory phases of;
See also
- Cathedral Peak Granodiorite
- El Capitan Granite
- Fine Gold Intrusive Suite
- Geology of the Yosemite area
- Intrusive Suite of Buena Vista Crest
- Intrusive Suite of Merced Peak
- Intrusive Suite of Sonora Pass
- Kuna Crest Granodiorite
- Porphyry
- Sentinel granodiorite
- Tuolumne Intrusive Suite
References
- ^ Calkins, Frank C. "The Granitic Rocks of the Yosemite Region".
- Glazner, Allen F, Stock, Greg M. (2010). Geology Underfoot in Yosemite. Mountain Press, p. 53. ISBN 978-0-87842-568-6.
- Bracciali, Laura; Paterson, Scott R.; Memeti, Vali; Rocchi, Sergio; Matzel, J.; Mundil, Roland (2008). "Build-up of the Tuolumne Batholith, California: the Johnson Granite Porphyry" (published January 1, 2008).
- Calkins, F.C. (1930). "National Geologic Map Database".
- ^ Bracciali, Laura; Memeti, Vali; Paterson, Scott R.; Rocchi, Sergio (January 2008). "Build-up of the Tuolumne Batholith, California: the Johnson Granite Porphyry". ResearchGate.
- Bracciali, Laura; Paterson, Scott; Memeti, Valbone; Rocchi, Sergio; Matzel, Jennifer; Mundil, Roland (2008). "Build-up of the Tuolumne Batholith, California: the Johnson Granite Porphyry".
- Titus, Sarah J.; Clark, Ryan; Tikoff, Basil (September 2005). "Geologic and geophysical investigation of two fine-grained granites, Sierra Nevada Batholith, California: Evidence for structural controls on emplacement and volcanism". Geological Society of America Bulletin.
{{cite web}}: CS1 maint: date and year (link) - Titus, S.; Clark, R.; Tikoff, S. (September 1, 2005). "Geologic and geophysical investigation of two fine-grained granites, Sierra Nevada Batholith, California: Evidence for structural controls on emplacement and volcanism". Geological Society of America Bulletin. 117 (9): 1256. doi:10.1130/B25689.1. S2CID 129298834.
External links and references
- Reference with a photo
- Geologic and geophysical investigation of two fine-grained granites, Sierra Nevada Batholith, California: Evidence for structural controls on emplacement and volcanism
- National Geologic Map Database site